Programmable particle scatterer for radiation therapy beam formation

ABSTRACT

Interposing a programmable path length of one or more materials into a particle beam modulates scattering angle and beam range in a predetermined manner to create a predetermined spread out Bragg peak at a predetermined range. Materials can be “low Z” and “high Z” materials that include fluids. A charged particle beam scatterer/range modulator can comprise a fluid reservoir having opposing walls in a particle beam path and a drive to adjust the distance between the walls of the fluid reservoir under control by a programmable controller. A “high Z” and, independently, a “low Z” reservoir, arranged in series, can be used. When used for radiation treatment, the beam can be monitored by measuring beam intensity, and the programmable controller can adjust the distance between the opposing walls of the “high Z” reservoir and, independently, the distance between the opposing walls of the “low Z” reservoir according to a predetermined relationship to integral beam intensity. Beam scattering and modulation can be done continuously and dynamically during a treatment in order to deposit dose in a target volume in a predetermined three dimensional distribution.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/590,088, filed on Jul. 21, 2004. The entire teachings of the aboveapplication are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Charged particles have been used in the field of radiation therapy forcancer for more than 50 years. In order to create a clinically usefuldose distribution that conforms to the shape of the target volume withinthe patient, a number of beam shaping and modulating materials areinterposed between the particle accelerator and the patient. A protonbeam has a significant clinical advantage over conventional high energyx-ray beams which attenuate exponentially in tissue. The physics of theenergy deposition is advantageous and different for protons compared tohigh energy x-rays (photons).

A proton beam delivers a small entrance dose, then delivers a large doseas the protons stop in the tissue. This large deposition of dose at theend of the tissue penetration range of the protons is called a Braggpeak, after the physicist who discovered the effect. FIG. 1 shows theBragg peak from an unmodulated beam, as well as a spread out Bragg peakand the series of individual Bragg peaks that add together to make thespread out Bragg peak.

The beam, emerging from the particle accelerator, is shaped by insertingdevices and materials into the beam. One objective of shaping the beamis to deliver a uniform dose of radiation throughout the volume of atarget, such as a tumor in a patient's body. The range (i.e. the depthof beam penetration into the tissue) needs to be modulated to ensurethat a uniform or other predetermined dose of radiation is deliveredbetween the proximal and the distal surfaces of the target. (As usedherein, the terms “proximal” and “distal” are used with respect to thebeam path. The term “proximal” specifically refers to the area of entryof a beam into a target.) Furthermore, the beam needs to be spread outlaterally in order to treat large tumors. (As used herein, the terms“lateral” refers to any direction substantially perpendicular to thebeam path.) The beam is manipulated and shaped by a series of scatterersand apertures.

In a beam shaping system, the beam is first directed at a firstscatterer/range modulator, which scatters the proton beam through anangle wide enough to treat a therapy field of about 20-30 cm. Followingscattering and range modulation by the first scatterer, the beam isdirected to a compensated second scatterer. The purpose of this elementis to flatten the cross section of the beam emerging from the firstscatterer. This allows the Bragg peak to be planar and uniform inintensity at the isocenter distance. FIG. 2 shows a compensated secondscatterer that is comprised of high Z and low Z materials with shapesthat match the scattering property of the high Z material with theabsorption properties of the low Z material in order to provide a flat,uniform broad beam.

The third element of the beam shaping system is a range matching bolus.This is typically a thick cylinder of acrylic plastic into which theinverse of the 3-dimensional shape of the distal surface of the targetvolume has been machined. This element also includes a correction forthe profile of the external surface of the patient from the beamdirection and a correction for the inhomogenieties such as bone or airin the path. Most tissue is substantially equivalent to water, butcorrections for these different materials can be calculated from the CTimage data set. The resulting three dimensional structure is placed inthe beam path to ensure that the Bragg peak conforms to the distalsurface of the target, resulting in minimum dose to critical structureslocated beyond the target volume.

The fourth element of the beam shaping system shapes the beam laterallyto match the shape of the target volume as seen from the direction ofthe beam's origin by using apertures made specifically for thattreatment. This is usually accomplished by machining a profiled apertureinto a thick piece of brass or other high Z material and placing it inclose proximity to the patient. The beam is limited in lateral extent bythis element and therefore conforms to the shape of the target volume.

SUMMARY OF THE INVENTION

Interposing a programmable path length of one or more scattering and/orabsorbing materials into a particle beam may be used to modulatescattering angle and beam range in a predetermined manner. A chargedparticle beam scatterer/range modulator can comprise high Z material,having an adjustable path length in a particle beam path, low Z materialhaving an adjustable path length in the particle beam path, and aprogrammable controller that independently adjusts the high Z and low Zpath lengths during exposure of a target to the beam. The high Z and thelow Z materials can be liquid. The path length of the low Z materialand, independently, the path length of the high Z material can becontinuously adjustable.

The charged particle beam scatterer/range modulator can comprise a fluidreservoir having opposing walls in a particle beam path, a drive toadjust the distance between the walls of the fluid reservoir, and aprogrammable controller for the drive to adjust the distance between thewalls of the reservoir during exposure of a target to the beam. Thedistance between the opposing walls of the reservoir can be continuouslyadjustable. A first and second fluid reservoir can be arranged in seriesin the particle beam path. The first and the second reservoirs canindependently contain high Z and low Z materials. The distance betweenthe opposing walls of the first reservoir and, independently, thedistance between the opposing walls of the second reservoir can becontinuously adjustable.

A source of charged particles that provides a charged particle beam anda charged particle beam scatterer/range modulator can be employed in aradiation treatment apparatus. A beam monitor can be used to measurebeam intensity and communicate beam intensity to the programmablecontroller. The programmable controller can adjust the low Z and,independently, the high Z path lengths according to a predeterminedrelationship between the time integral of the beam intensity and thedesired path lengths of the low Z and high Z materials. The programmablecontroller can adjust the low Z and, independently, the high Z pathlengths continuously and dynamically.

The source of charged particles can be a cyclotron. The cyclotron can bea synchrocyclotron. Any charged particles may be used, for example, thecharged particles can be protons.

The high Z material and the low Z material of a charged particle beamscatterer/range modulator can be disposed in an extraction channel ofthe synchrocyclotron. Where the charged particle beam scatterer/rangemodulator comprises a fluid reservoir, having opposing walls in aparticle beam path, such fluid reservoir can similarly be disposed in anextraction channel of the synchrocyclotron.

Embodiments of the present invention have a number of advantages. Byindependently and continuously changing thicknesses of high Z and low Zmaterial, the path of the particle can be varied continuously over thecourse of a treatment. This can effectively produce uniquely variable,substantially arbitrary profiles of spread out Bragg peaks, thusdelivering both a conformal and a non-uniform dose of radiation to thetarget. The first scatterer/range modulator of the present inventionmatches the dose deposition by the beam to the treatment volume in threedimensions, resulting in a highly conforming dose distribution. Thisleads to the best clinical outcome for the patient. The local controlrate of the cancer treatment increases with increasing dose to thetumor, while the complication rate (due to unnecessary dose to criticalstructures) increases with the dose given to the surrounding normaltissue. By using a precisely shaped proton beam, the ratio of treatmentvolume dose to the dose given to surrounding tissue is increasedmarkedly over treatments given with photon (x-ray) beams.

The use, in some embodiments, of synchrocyclotron as a source of chargedparticles allows the present invention to avoid relying on a variableenergy beam. Furthermore, the operation of the device of the presentinvention can be controlled by a programmable processor in acontinuously variable manner by adjusting the timing of the motion ofthe high Z and low Z materials to generate a predetermined, non-uniformspread out Bragg peak.

In addition to the regular clinical scenarios, there is at least onespecial case of scattering and range modulation where a higherintensity, small beam is required, such as in the case of treating eyetumors or macular degeneration. These special cases have a shallow depthof penetration, a very small field size and the treatment time is to beminimized. In this case, the second compensated scatterer is notemployed, as the field size is very small. The first scatterer/rangemodulator of the instant invention is particularly advantageous for thisspecial case application.

This invention uses the underlying physical principles employed in thepast and combines them with modern control system technology and a novelgeometry to create a novel beam scattering and range modulationapparatus that can programmatically deliver not only the sameperformance as fixed scatterer/modulator components, but also uniquelyvariable profiles modulated in time to generate dose distributions thatcan be more highly conformal to the target volume. The ability tocontinuously and independently vary the beam path lengths through the“high Z” and “low Z” materials avoids the problem of having to plan anddeliver a treatment does of radiation in a finite number of fixed spreadout Bragg peaks.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1A is a representative plot showing the deposited dose of radiationdelivered by a proton beam as a function of depth of penetration. Thepeak at the distal portion of the range of penetration is the Braggpeak.

FIG. 1B is a plot that shows a “spread out” Bragg peak that is desiredfor delivery of a conformal dose of radiation.

FIG. 1C is a plot that shows the result of superposition of severalBragg peaks produced by proton beams with modulated range ofpenetration.

FIG. 2 shows the cross-section of a compensated second scatterer that iscomprised of high Z and low Z materials with shapes that match thescattering and absorption properties of the materials.

FIG. 3 is a block-diagram of a radiation treatment system that employsdevices and methods of the present invention.

FIG. 4A is a side view (partially cut away) of the preferred embodimentof a charged particle scatterer/range modulator of the presentinvention.

FIG. 4B is an end view of the device of FIG. 4A.

FIG. 5A is a is a side view (partially cut away) of a variation in thepreferred embodiment of a charged particle scatterer/range modulator ofthe present invention.

FIG. 5B is an end view of the device of FIG. 6A.

FIG. 6 is a plan view showing the advantageous positioning of theembodiment shown in FIG. 5A when combined with a particle accelerator.

FIG. 7 is a block-diagram illustrating the feedback control loopemployed by the preferred embodiment of a method of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Although this invention is applicable to all charged particle beams,this discussion will focus on proton beams for radiation therapy as anillustrative and advantageous example.

As discussed above, the proton beam emerging from a particle acceleratoris shaped and modulated by a number of devices and material interposedin the beam path.

An embodiment of the present invention is a charged particlescatterer/range modulator, that, in some embodiments, can be used incommon implementations of proton beam radiation therapy systems as afirst scatterer. FIG. 3 is a block diagram of proton therapy system 100incorporating embodiments of the present invention. It is simplified toillustrate the elements of the system that pertain to this invention.Other subsystems such as RF control system of the particle accelerator,vacuum, power supplies, etc. have been omitted for clarity.

The input 102 into the system 100 is, typically, the size and locationof the target volume to be treated and the external contour of thepatient. Target volume parameters 102 are used by the treatment planningsystem 104 to prescribe a three dimensional dose distribution toconformally deliver the dose to the target volume. The output oftreatment planning system 104 is communicated to the proton therapysystem controller 106, that generates a series of parameters used bydifferent subsystems to implement the treatment. These parametersinclude distal extent of Bragg peak and depth of spread out Bragg peak108 and calculations 110 of high and low Z path lengths as a function ofintegral dose, which are based on parameters 108. The parametersimportant to the subsystem comprising the programmable firstscatterer/range modulator 112 are the path length of high and low Zmaterial to be interposed into the proton beam as a function of integraldose as measured by the beam monitor 114. If the output of theaccelerator 116 was known to be constant over time, the path lengthcould be programmed with respect to time. In this embodiment, use of theinformation directly from the beam monitor 114 removes the constraintthat the output of the accelerator be constant with time.

The calculated path lengths with corrections for the measured integraldose, are converted by first scatterer/range modulator control system118 into high Z and low Z position commands 120 for linear actuators 122and 123 that vary the path lengths 124 and 125 of the high Z and low Zmaterials, respectively. The high Z and low Z materials can be solid,liquid or gaseous. Liquid materials are preferred. In a preferredembodiment, linear actuators 122 and 123 are linear motors/encoders. Theencoders measure the actual position and servo loops within the system(shown in greater detail with reference to FIG. 7) ensure tight controland error condition sensing to ensure safety and prevent errors intreatment by exercising tight control of low Z and high Z path lengths.

Beam 126, produced by particle accelerator 116, which, in oneembodiment, is a cyclotron, is monitored by beam monitor 114 andmodulated by the first scatterer/range modulator of the presentinvention 112. After passing through the first scatterer 112, beam 126passes through the second compensated scatterer 128, such as the oneshown in FIG. 2.

Following continuing lateral expansion and beam conditioning at thesecond scatterer 128, beam 126 is further shaped by range compensatingbolus 130 and, laterally, by final conformal aperture 132 beforeentering target volume 134 within patient 136.

Two alternative embodiments of first scatterer/range modulator 112 ofFIG. 3 are devices 200 and 200′, shown in FIGS. 4A and 4B and FIGS. 5Aand 5B.

Referring to FIGS. 4A and 5A, devices 200 and 200′ comprise two sealedsystems: system 202, filled with a low Z fluid, such as water, andsystem 204 filled with a high Z fluid, such as mercury in liquid state.The fluids cam also incorporate other elements in solution such as boronin the low Z fluid that may act as shielding for neutrons produced inthe high Z section. The proton beam (not shown) travels along axis 208from left to right. The two systems 202 and 204 are arranged in series.Either the high Z system 204 or the low Z system 202 can be locatednearest to the source of the proton beam. The embodiments shown herehave the high Z system 204 located nearest the output of the accelerator116 (see FIG. 3 or FIG. 6).

To provide reliable fluid sealing over a long life, the systems 202 and204 include welded metal bellows 212 and 214, respectively. Bellows 212and 214 function as expandable side walls that, together with theopposing walls 216, 218 (system 202) and 220, 222 (system 204), formfluid reservoirs of adjustable volume disposed in a particle beam path.Referring to device 200 as shown in FIG. 4A, within each reservoir,there are re-entrant tubular extensions 224 and 226. Referring to device200′ as shown in FIG. 5A, the tubular extensions 224′ and 226′ arecoaxial, with tubular extension 226′ disposed within tubular extension224′. Referring to device 200′ as shown in FIG. 5A, opposing walls 216and 222 are different surfaces of the same portion of tubular extension226′. Side wall 220 holds entrance window 228. Side wall 218 holds exitwindow 230. The entrance and exit windows 228 and 230 are made of thinradiation-resistant foil made of, for example, stainless steel ortitanium. The foil is thin enough to not substantially affect the beam.

Referring to device 200 as shown in FIG. 4A, a thin, radiation resistantseptum 232, made from material similar to those of windows 228 and 230,is disposed across an aperture within central plate 234. Referring todevice 200′, as shown in FIG. 5A, septum 232′ is disposed across anaperture in the portion of tubular extension 226′ that defines walls 216and 222. Septum 232 separates the two fluids in systems 202 and 204. Asmall correction for the thickness of septum 232 and windows 228, 230would be accounted for in the modeling of the system.

Referring to device 200 as shown in FIG. 4A, during the operation of thebellows 212 and 214, entrance and exit windows 228 and 230 can touch thedividing septum 232. Likewise, referring to device 200′ as shown in FIG.5A, entrance and exit windows 228 and 230 can touch the dividing septum232′. This allows either the high Z path length or, independently, thelow Z path length to be chosen as substantially zero. An allowance forfurther compression of the bellows 212 and 214 is made to allow theentrance and exit windows 228 and 230 to touch the dividing septum 232or 232′ before the bellows 212 and 214 are fully compressed.

Linear bearings rail 240 constrains the motion of the bellows 212 and214 and extensions 226, 226′ and 224, 224′ to be substantially co-linearwith the particle beam axis 208.

A pair of linear motors/encoder, such as actuators 122 and 124 shown inFIG. 3, are used to change low Z and high Z path lengths. Referring toFIGS. 4A and 5A, the linear motors/encoders include stators 242 and 244,substantially parallel to beam axis 208, and motor/encoders carriages246 and 248 that move along stators 242, 244. Attached to motor/encodercarriage 246 and to low Z bellows 212 is ball bearing carriage 250 thatmoves along linear rail 240 using ball bearings 252. Similarly, ballbearing carriage 254 is attached to motor/encoder carriage 248 and tohigh Z bellows 214. Ball bearing carriage 254 moves along linear rail240 using ball bearings 256. Movement of motor/encoder carriages 246 and248 expands or contracts bellows 212 and 214, changing the amounts ofhigh Z and low Z fluids filling the respective bellows and thus changingthe high Z and low Z path lengths.

The fluids in the bellows are substantially incompressible. Therefore,provision is made for a set of expansion reservoirs, also constructed ofwelded metal bellows in this embodiment. Referring to FIGS. 4B and 5B,expansion reservoirs 270 and 272 are adjacent to bellows 212 and 214.Expansion reservoirs 270 and 272 are connected by way of internalpassages 274 in the central plate 234. As the path length of eitherfluid is varied by means of the control system 118, the displaced fluidis accommodated in the corresponding expansion reservoir. The drivenbellows 212 and 214 and the expansion reservoirs 270 and 272 comprise asealed system with no sliding or wearing seals that tend to deteriorateand leak over time and in proximity to scattered radiation. Thereliability of the sealed systems can be predicted from the fatigueproperties of the materials chosen for the bellows and can be madeeffectively infinite if the design stress does not exceed the endurancelimit of the material. This is important when using a material such asmercury in a hospital environment.

Referring to FIG. 6, by nesting tubular extensions 224′ and 226′ ofdevice 200′ as shown in FIG. 5A, the scattering fluids can be placedcloser to a particle beam source, such as accelerator 116, thanotherwise would be possible for device 200. As shown in FIG. 6, tubularextensions 224′ and 226′ can be inserted into extraction channel 701,allowing a more compact overall system. It is noted that tubularextensions 224′ and 226′ are preferably magnetically shielded. Theprinciples of operation and the function of individual elements of theunit are identical to the embodiment shown in FIGS. 4A and 4B.

Referring again to FIG. 3, control system 118 drives the motors 122 and123 and receives signals from the motor/encoder carriages (246 and 248on FIGS. 4A and 5A) to precisely control the position and velocity ofthe entrance and exit windows 228, 230 with respect to septum 232 (seeFIGS. 4A and 5A). This translates into controlling the amount of high Zand low Z material in the path of the particle beam, thus controllingthe scattering angle and range of the particle beam in a pre-determinedmanner. The path lengths of high Z and low Z material 124 and 125, andtherefore the positions of the motor/encoder carriages (246 and 248 inFIGS. 4A and 5A) are also a function of integral dose or radiation,measured by the beam monitor 114. Accordingly, one embodiment, thepresent invention includes a feedback control loop 300, shown in FIG. 7.

Referring to FIG. 7, the integral dose of delivered radiation iscomputed at step 302 based on measurements by beam monitor 114. Based onthe integral dose, first scatterer/range modulator control system 118produces high Z and low Z position commands at steps 120 a and 120 b,respectively. These commands are transmitted to linear actuators/motors(122 and 123 in FIG. 3), which change the positions of high Z and low Zmotor carriages/encoders (246 and 248 in FIGS. 4A and 5A). At steps 304a and 304 b, the encoders measure the actual position of the carriagesand transmit this data to first scatterer/range modulator control 118.Thus, feedback control loop 300 is used, in response to beam intensityoutput, to continuously, dynamically (i.e. in real time) andindependently adjust the distance between entrance window 228 and septum232 within high Z system 204 and septum 232 and exit window 230 withinlow Z system 202 (see FIGS. 4A and 5A). Accordingly, the low Z and thehigh Z path lengths are continuously, dynamically and independentlyadjusted according to beam intensity.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A charged particle beam scatterer/range modulator comprising: high Zmaterial having an adjustable path length in a particle beam path; low Zmaterial having an adjustable path length in the particle beam path; anda programmable controller that independently adjusts the high Z and lowZ path lengths during exposure of a target to the beam.
 2. Thescatterer/modulator of claim 1 wherein the high Z and the low Zmaterials are liquid.
 3. The scatterer/modulator of claim 1 wherein thepath length of the low Z material and, independently, the path length ofthe high Z material are continuously adjustable.
 4. Thescatterer/modulator of claim 1 wherein the charged particles areprotons.
 5. A radiation treatment apparatus, comprising: a source ofcharged particles that provides a charged particle beam; and a chargedparticle beam scatterer/range modulator, that includes high Z materialhaving an adjustable path length in a particle beam path; low Z materialhaving an adjustable path length in the particle beam path; and aprogrammable controller that independently adjusts the high Z and low Zpath lengths during exposure of a target to the beam.
 6. The apparatusof claim 5 wherein the high Z and the low Z materials are liquid.
 7. Theapparatus of claim 5 wherein the path length of the low Z material and,independently, the path length of the high Z material are continuouslyadjustable.
 8. The apparatus of claim 5 wherein the charged particlesare protons.
 9. The apparatus of claim 5 wherein the source is acyclotron.
 10. The apparatus of claim 9 wherein the cyclotron is asynchrocyclotron.
 11. The apparatus of claim 5 further including a beammonitor for measuring particle beam intensity, the beam monitorcommunicating beam intensity to the programmable controller, theprogrammable controller adjusting the low Z and, independently, the highZ path lengths according to integral beam intensity.
 12. The apparatusof claim 11 wherein the programmable controller adjusts the low Z and,independently, the high Z path lengths continuously and dynamically. 13.A method of scattering and/or modulating a range of a changed particlebeam, comprising: directing a charged particle beam through a high Zmaterial having an adjustable path length in a particle beam path;directing the charged particle beam through a low Z material having anadjustable path length in the particle beam path; and independentlyadjusting the high Z and low Z path lengths during exposure of a targetto the beam under control by a programmable controller.
 14. The methodof claim 13 wherein the high Z and the low Z materials are liquid. 15.The method of claim 13 wherein the path length of the low Z materialand, independently, the path length of the high Z material arecontinuously adjustable.
 16. The apparatus of claim 13 wherein thecharged particles are protons.
 17. The method of claim 13 furtherincluding measuring particle beam intensity; and with the programmablecontroller adjusting the low Z and, independently, the high Z pathlengths according to beam intensity.
 18. The method of claim 17 whereinthe programmable controller adjusts the low Z and, independently, thehigh Z path lengths continuously and dynamically.
 19. A method oftreating a patient by directing a charged particle beam at a targetwithin said patient, comprising: producing a charged particle beam;directing the charged particle beam through a high Z material having anadjustable path length in a particle beam path; directing the chargedparticle beam through a low Z material having an adjustable path lengthin the particle beam path; and independently adjusting the high Z andlow Z path lengths during exposure of a target to the beam under controlby a programmable controller.
 20. The method of claim 19 wherein thehigh Z and the low Z materials are liquid.
 21. The method of claim 19wherein the path length of the low Z material and, independently, thepath length of the high Z material are continuously adjustable.
 22. Themethod of claim 19 wherein the charged particles are protons.
 23. Themethod of claim 19 wherein the charged particle beam is produced by acyclotron.
 24. The method of claim 23 wherein the cyclotron is asynchrocyclotron.
 25. The method of claim 19 further including measuringbeam intensity; and with the programmable controller adjusting the low Zand, independently, the high Z path lengths according to beam intensity.26. A charged particle beam scatterer/range modulator comprising: afluid reservoir having opposing walls in a particle beam path; a driveto adjust the distance between the walls of the fluid reservoir; and aprogrammable controller for the drive to adjust the distance between thewalls of the reservoir during exposure of a target to the beam.
 27. Thescatterer/modulator of claim 26 wherein the distance between theopposing walls of the reservoir is continuously adjustable.
 28. Thescatterer/modulator of claim 27 comprising a first and a second fluidreservoirs arranged in series in the particle beam path.
 29. Thescatterer/modulator of claim 28 wherein the distance between theopposing walls of the first reservoir and, independently, the distancebetween the opposing walls of the second reservoir are continuouslyadjustable.
 30. The scatterer/modulator of claim 29 further including ahigh Z material within the first reservoir and a low Z material withinthe second reservoir.
 31. The scatterer/modulator of claim 26 whereinthe charged particles are protons.
 32. A radiation treatment apparatus,comprising: a source of charged particles that provides a chargedparticle beam; and a charged particle beam scatterer/range modulatorthat includes a fluid reservoir having opposing walls in a particle beampath; a drive to adjust the distance between the walls of the reservoir;and a programmable controller for the drive to adjust the distancebetween the walls of the reservoir during exposure of a target to thebeam.
 33. The apparatus of claim 32 wherein the distance between theopposing walls of the reservoir is continuously adjustable.
 34. Theapparatus of claim 33 comprising a first and a second reservoirsarranged in series in the particle beam path.
 35. The apparatus of claim34 wherein the distance between the opposing walls of the firstreservoir and, independently, the distance between the opposing walls ofthe second reservoir are continuously adjustable.
 36. The apparatus ofclaim 35 further including a high Z material within the first reservoirand a low Z material within the second reservoir.
 37. The apparatus ofclaim 35 wherein the charged particles are protons.
 38. The apparatus ofclaim 37 wherein the source is a cyclotron.
 39. The apparatus of claim38 wherein the cyclotron is a synchrocyclotron.
 40. The apparatus ofclaim 35 further including a beam monitor for measuring particle beamintensity, the programmable controller adjusting the distance betweenthe opposing walls of the first reservoir and, independently, thedistance between the opposing walls of the second reservoir according tobeam intensity.
 41. The apparatus of claim 40 wherein the programmablecontroller adjusts distance between the opposing walls of the firstreservoir and, independently, the distance between the opposing walls ofthe second reservoir continuously and dynamically.
 42. A method oftreating a patient by directing a charged particle beam at a targetwithin said patient, comprising: producing a charged particle beam;directing the charged particle beam through a fluid reservoir havingopposing walls in a particle beam path; adjusting the distance betweenopposing walls of the fluid reservoir during exposure of a target to thebeam under control of a programmable controller.
 43. The method of claim42 wherein the charged particle beam is directed through a first and asecond reservoirs arranged in series in the particle beam path.
 44. Themethod of claim 43 further including continuously adjusting the distancebetween the opposing walls of the first reservoir and, independently,the distance between the opposing walls of the second reservoir.
 45. Themethod of claim 44 further including measuring beam intensity; andcommunicating beam intensity to the programmable controller, wherein theprogrammable controller adjusts the distance between the opposing wallsof the first reservoir and, independently, the distance between theopposing walls of the second reservoir according to beam intensity. 46.The method of claim 45 wherein the first reservoir contains a high Zmaterial within and the second reservoir contains a low Z material. 47.The method of claim 42 wherein the charged particles are protons. 48.The method of claim 42 wherein the charged particle beam is produced bya cyclotron.
 49. The method of claim 48 wherein the cyclotron is asynchrocyclotron.
 50. A radiation treatment apparatus, comprising: asynchrocyclotron that provides a charged particle beam; and a chargedparticle beam scatterer/range modulator, that includes high Z materialin an extraction channel of the synchrocyclotron having an adjustablepath length in a particle beam path; low Z material in an extractionchannel of the synchrocyclotron having an adjustable path length in theparticle beam path; and a programmable controller that independentlyadjusts the high Z and low Z path lengths during exposure of a target tothe beam.
 51. The apparatus of claim 50 wherein the high Z and the low Zmaterials are liquid.
 52. The apparatus of claim 50 wherein the pathlength of the low Z material and, independently, the path length of thehigh Z material are continuously adjustable.
 53. The apparatus of claim50 wherein the charged particles are protons.
 54. The apparatus of claim50 further including a beam monitor for measuring particle beamintensity, the beam monitor communicating beam intensity to theprogrammable controller, the programmable controller adjusting the low Zand, independently, the high Z path lengths according to integral beamintensity.
 55. The apparatus of claim 54 wherein the programmablecontroller adjusts the low Z and, independently, the high Z path lengthscontinuously and dynamically.
 56. A method of scattering and/ormodulating a range of a changed particle beam, comprising: producing aparticle beam in a synchrocyclotron; directing the charged particle beamthrough a high Z material having an adjustable path length in a particlebeam path and disposed in an extraction channel of the synchrocyclotron;directing the charged particle beam through a low Z material having anadjustable path length in the particle beam path and disposed in theextraction channel of the synchrocyclotron; and independently adjustingthe high Z and low Z path lengths during exposure of a target to thebeam under control by a programmable controller.
 57. The method of claim56 wherein the high Z and the low Z materials are liquid.
 58. The methodof claim 56 wherein the path length of the low Z material and,independently, the path length of the high Z material are continuouslyadjustable.
 59. The apparatus of claim 56 wherein the charged particlesare protons.
 60. The method of claim 56 further including measuringparticle beam intensity; and with the programmable controller adjustingthe low Z and, independently, the high Z path lengths according to beamintensity.
 61. The method of claim 60 wherein the programmablecontroller adjusts the low Z and, independently, the high Z path lengthscontinuously and dynamically.
 62. A radiation treatment apparatus,comprising: a synchrocyclotron that provides a charged particle beam;and a charged particle beam scatterer/range modulator that includes afluid reservoir disposed in an extraction channel of thesynchrocyclotron and having opposing walls in a particle beam path; adrive to adjust the distance between the walls of the reservoir; and aprogrammable controller for the drive to adjust the distance between thewalls of the reservoir during exposure of a target to the beam.
 63. Theapparatus of claim 62 wherein the distance between the opposing walls ofthe reservoir is continuously adjustable.
 64. The apparatus of claim 63comprising a first and a second reservoirs arranged in series in theparticle beam path.
 65. The apparatus of claim 64 wherein the distancebetween the opposing walls of the first reservoir and, independently,the distance between the opposing walls of the second reservoir arecontinuously adjustable.
 66. The apparatus of claim 65 further includinga high Z material within the first reservoir and a low Z material withinthe second reservoir.
 67. The apparatus of claim 65 wherein the chargedparticles are protons.
 68. The apparatus of claim 65 further including abeam monitor for measuring particle beam intensity, the programmablecontroller adjusting the distance between the opposing walls of thefirst reservoir and, independently, the distance between the opposingwalls of the second reservoir according to beam intensity.
 69. Theapparatus of claim 68 wherein the programmable controller adjustsdistance between the opposing walls of the first reservoir and,independently, the distance between the opposing walls of the secondreservoir continuously and dynamically.